[RFC v2 2/2] rng: Provide a RNG based on the RISC-V Zkr ISA extension

[merle w]

drivers/rng/riscv_zkr_rng.c:10:10: fatal error: interrupt.h: No such
file or directory
10 | #include <interrupt.h>
| ^~~~~~~~~~~~~
compilation terminated.

Where is this interrupt.h?

Regards,
Xiang W

Heinrich Schuchardt <heinrich.schuchardt at canonical.com> 于2023年10月29日周日 16:46写道：
>
> The Zkr ISA extension (ratified Nov 2021) introduced the seed CSR. It
> provides an interface to a physical entropy source.
>
> A RNG driver based on the seed CSR is provided. It depends on
> mseccfg.sseed being set in the SBI firmware.
>
> Signed-off-by: Heinrich Schuchardt <heinrich.schuchardt at canonical.com>
> ---
> v2:
>         Resume after exception if seed CSR cannot be read.
> ---
>  drivers/rng/Kconfig         |   8 +++
>  drivers/rng/Makefile        |   1 +
>  drivers/rng/riscv_zkr_rng.c | 116 ++++++++++++++++++++++++++++++++++++
>  3 files changed, 125 insertions(+)
>  create mode 100644 drivers/rng/riscv_zkr_rng.c
>
> diff --git a/drivers/rng/Kconfig b/drivers/rng/Kconfig
> index 994cc35b27..4f6e367169 100644
> --- a/drivers/rng/Kconfig
> +++ b/drivers/rng/Kconfig
> @@ -48,6 +48,14 @@ config RNG_OPTEE
>           accessible to normal world but reserved and used by the OP-TEE
>           to avoid the weakness of a software PRNG.
>
> +config RNG_RISCV_ZKR
> +       bool "RISC-V Zkr random number generator"
> +       depends on RISCV_SMODE
> +       help
> +         This driver provides a Random Number Generator based on the
> +         Zkr RISC-V ISA extension which provides an interface to an
> +         NIST SP 800-90B or BSI AIS-31 compliant physical entropy source.
> +
>  config RNG_STM32
>         bool "Enable random number generator for STM32"
>         depends on ARCH_STM32 || ARCH_STM32MP
> diff --git a/drivers/rng/Makefile b/drivers/rng/Makefile
> index 47b323e61e..a5d3ca4130 100644
> --- a/drivers/rng/Makefile
> +++ b/drivers/rng/Makefile
> @@ -10,6 +10,7 @@ obj-$(CONFIG_RNG_MSM) += msm_rng.o
>  obj-$(CONFIG_RNG_NPCM) += npcm_rng.o
>  obj-$(CONFIG_RNG_OPTEE) += optee_rng.o
>  obj-$(CONFIG_RNG_STM32) += stm32_rng.o
> +obj-$(CONFIG_RNG_RISCV_ZKR) += riscv_zkr_rng.o
>  obj-$(CONFIG_RNG_ROCKCHIP) += rockchip_rng.o
>  obj-$(CONFIG_RNG_IPROC200) += iproc_rng200.o
>  obj-$(CONFIG_RNG_SMCCC_TRNG) += smccc_trng.o
> diff --git a/drivers/rng/riscv_zkr_rng.c b/drivers/rng/riscv_zkr_rng.c
> new file mode 100644
> index 0000000000..8c9e111e2e
> --- /dev/null
> +++ b/drivers/rng/riscv_zkr_rng.c
> @@ -0,0 +1,116 @@
> +// SPDX-License-Identifier: GPL-2.0-or-later
> +/*
> + * The RISC-V Zkr extension provides CSR seed which provides access to a
> + * random number generator.
> + */
> +
> +#define LOG_CATEGORY UCLASS_RNG
> +
> +#include <dm.h>
> +#include <interrupt.h>
> +#include <log.h>
> +#include <rng.h>
> +
> +#define DRIVER_NAME "riscv_zkr"
> +
> +enum opst {
> +       /** @BIST: built in self test running */
> +       BIST = 0b00,
> +       /** @WAIT: sufficient amount of entropy is not yet available */
> +       WAIT = 0b01,
> +       /** @ES16: 16bits of entropy available */
> +       ES16 = 0b10,
> +       /** @DEAD: unrecoverable self-test error */
> +       DEAD = 0b11,
> +};
> +
> +static unsigned long read_seed(void)
> +{
> +       unsigned long ret;
> +
> +       __asm__ __volatile__("csrrw %0, seed, x0" : "=r" (ret) : : "memory");
> +
> +       return ret;
> +}
> +
> +static int riscv_zkr_read(struct udevice *dev, void *data, size_t len)
> +{
> +       u8 *ptr = data;
> +
> +       while (len) {
> +               u32 val;
> +
> +               val = read_seed();
> +
> +               switch (val >> 30) {
> +               case BIST:
> +                       continue;
> +               case WAIT:
> +                       continue;
> +               case ES16:
> +                       *ptr++ = val & 0xff;
> +                       if (--len) {
> +                               *ptr++ = val >> 8;
> +                               --len;
> +                       }
> +                       break;
> +               case DEAD:
> +                       return -ENODEV;
> +               }
> +       }
> +
> +       return 0;
> +}
> +
> +/**
> + * riscv_zkr_probe() - check if the seed register is available
> + *
> + * If the SBI software has not set mseccfg.sseed=1 or the Zkr
> + * extension is not available this probe function will result
> + * in an exception. Currently we cannot recover from this.
> + *
> + * @dev:       RNG device
> + * Return:     0 if successfully probed
> + */
> +static int riscv_zkr_probe(struct udevice *dev)
> +{
> +       struct resume_data resume;
> +       int ret;
> +       u32 val;
> +
> +       /* Check if reading seed leads to interrupt */
> +       set_resume(&resume);
> +       ret = setjmp(resume.jump);
> +       if (ret)
> +               log_debug("Exception %ld reading seed CSR\n", resume.code);
> +       else
> +               val = read_seed();
> +       set_resume(NULL);
> +       if (ret)
> +               return -ENODEV;
> +
> +       do {
> +               val = read_seed();
> +               val >>= 30;
> +       } while (val == BIST || val == WAIT);
> +
> +       if (val == DEAD)
> +               return -ENODEV;
> +
> +       return 0;
> +}
> +
> +static const struct dm_rng_ops riscv_zkr_ops = {
> +       .read = riscv_zkr_read,
> +};
> +
> +U_BOOT_DRIVER(riscv_zkr) = {
> +       .name = DRIVER_NAME,
> +       .id = UCLASS_RNG,
> +       .ops = &riscv_zkr_ops,
> +       .probe = riscv_zkr_probe,
> +};
> +
> +U_BOOT_DRVINFO(cpu_riscv_zkr) = {
> +       .name = DRIVER_NAME,
> +};
> --
> 2.40.1
>